A number of applications clearly show that water droplets projected at high velocity can retain their integrity until impacting on a desired target a selected distance away. For example, cutting machines using high pressure air and/or water jets have been successfully used for many years. Vaccination guns based on hydraulic propulsion have also become commonplace. Due to the number of conversions prior to application, energy is, however, not always utilised efficiently.
Direct energy conversion from electrical to kinetic has been applied in the case of metallic projectile launchers utilising a successively pulsed array of solenoid coils to provide the requisite accelerating force. It has also been applied in conjunction with a water propellant to effect the discharge of a small gun--the water first having been made conductive by the addition of salt--and by passing through an electrical current to bring about an electric arc, thereby promoting the requisite surge of electric current required to eject a solid projectile from the barrel at high velocity.
A water-arc launcher utilising this principle is described in a magazine article by Peter Graneau. Electronics and Wireless World, June 1989, pp 556-559. However, the side-mounted current connector in this version results in pronounced asymmetry in the axial current flow upon launching, causing the liquid charge to scatter widely upon emerging from the barrel, and thereby rendering the device ineffective for use as a globular liquid projectile launcher. The use of a solid projectile in conjunction with the water charge incorporated in the water gun featured in this article is also somewhat impractical. While the water charge amounts to a rather modest 3.8 g, the energy requirement to propel the total charge at 1000 meters per second would necessitate capacitor charge to a voltage sufficient to sustain an electric arc, amounting to a half to a full farad of capacitance, and capable of discharging in sizable fractions of 100 kA. This would weigh many kilograms, and make equipment based on this type of approach too heavy for use in applications requiring a high degree of portability.